A marking pen in which an ink is penetrated into a pen tip comprising a fibrous feed or a plastic feed so as to be writable has so far been used in many cases.
However, when a cap of such marking pen is taken away to leave a pen tip part standing in the air for long time, there involved is the problem in that the pen tip part is dried to cause inferior writing.
In the past, in a marking pen which is excellent in a cap-off performance of inhibiting drying at the pen tip, higher fatty acid esters of polyglycerin were added to inks (Japanese Patent Publication S62-34352/1987); paraffin waxes which can be deposited on the surface of a pen tip to form a thin film were added to inks (Japanese Patent Publication H01-35028/1989); hexaglyceryl tristearate was added to inks (Japanese Patent Application Laid-Open No. H02-232277/1990); and lecithin was added to inks (Japanese Patent No. 2594457).
However, many of additives having a high vaporization-inhibiting effect has a low solubility (10% by weight or less) in ink solvents and has a problem in terms of this low solubility. In particular, the solubility in the vicinity of 0° C. is low (5% by weight or less), whereby there involved are the problems in that precipitations of the additives described above are produced in the inks while pens are stored at a low temperature or exposed repeatedly to low and high temperatures, thereby causing clogging in the ink passages to reduce the writing property or deteriorate the cap-off property with the passage of time. Thus, the effective vaporization-inhibiting effect is not yet achieved.
Accordingly, the present inventors have filed a patent application for writing instruments such as a marking pen, a felt-tip pen and a writing brush pen having an excellent cap-off performance in which a pen tip comprising a fibrous feed or a plastic feed is coated with a substance providing a cap-off property (PCT Publication No. WO2000/37265).
These writing instruments in which a pen tip comprising a fibrous feed or a plastic feed is coated with a substance providing a cap-off property are excellent in a cap-off property but are not yet satisfactory, and it is the existing situation that writing instruments having a further better cap-off property are required.
Further, in marking pens for a writing board such as markers for a white board among marking pens, those in which pen tips comprising a fibrous feed or a plastic feed are coated with petroleum waxes such as paraffin wax as a substance providing a cap-off property have had a problem in terms of a little bad cap-off property as compared with other marking pens than those for a writing board in which pen tips are coated with petroleum waxes such as paraffin wax as a substance providing a cap-off property.
In light of the problems on the conventional techniques described above, the present invention intends to solve them, and an object thereof is to provide a marking pen having an excellent cap-off performance which provides a good writing performance even after the pen tip is left standing in the air over a long period of time.